Field of the Invention
The present invention relates to a method for driving a drive assembly in a drive system, the drive system having an automatic transmission and an automatic clutch that optionally couples the drive assembly to the transmission in order to transmit torque. The invention also relates to a drive system.
European Patent Application EP 0 695 665 B1, corresponding to U.S. Pat. No. 5,609,545, discloses such a drive system in which a first drive apparatus is assigned to the automatic drive assembly, and a second drive apparatus is assigned to the automatic transmission. These drive apparatuses exchange data and when a gearshift operation occurs, the first drive apparatus drives the drive assembly in such a way that the torque thereof is reduced from a starting value to a region of zero. During this reduction in torque, the control device provides for the automatic transmission any setpoint values that are transmitted to the control device of the drive assembly, which are to drive the drive assembly, in such a way that the deviation between the actual value of the torque and the setpoint value is minimized. However, this procedure does not take into account the fact that, on the one hand, the transmission of data between the two drive apparatuses leads to these values being provided with a delay in the drive device for the drive assembly, and that, moreover, the driving of the drive assembly, which is performed by the drive apparatus for the drive assembly in order to set a specific actual value, also takes place with a specific delay because, in particular, intervention into the throttle system of an internal combustion engine is a comparatively sluggish intervention whose reaction takes place with a certain delay. This leads to a situation in which in this known method or this known system there is a relatively large deviation between the actual torque of the drive assembly and the setpoint value predefined by the drive device for the automatic transmission, with the consequence that the desired gearshift characteristic often can no longer be obtained. German Published, Non-Prosecuted Patent Application DE 197 25 816 A1 discloses a method for driving an automatic torque transmission system in which a drive unit drives the drive assembly by reference to predefined setpoint values, the setpoint values being each determined directly from the operating state or a characteristic diagram during the execution of the gearshift operation. Thus, changing values of the torque are used, for example, as setpoint values of the respective nonspecific increment values or decrement values, the increment or decrement values of variables depending on variables, such as, for example, the pedal value, that is to say the depression of an accelerator pedal, the clutch slip and the like. Because these setpoint values for the torque are generated as a function of the actual operating state, they are available only for a relatively short period so that a specific time is necessary for adjusting the actual torque to the setpoint values which are then respectively predefined, with the consequence that here too an undesired delay occurs. This results in the actual torque following the setpoint torque with a specific delay and having a relatively large deviation from the setpoint torque.
It is accordingly an object of the invention to provide a drive system and method for driving a drive assembly in a drive system that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that provides a method for driving a drive assembly or a drive system with which the quality of the engine control can be improved when a gear is shifted.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for driving a drive assembly in a drive system. The method includes a first step of providing a drive system having an automatic transmission and an automatic clutch coupling the drive assembly to the automatic transmission for transmitting torque. The next step is sensing if a procedure having time segments is to be conducted. The next step is, after the procedure has been sensed, predefining a prediction profile for an operational variable characterizing an operating state of the drive assembly for at least one time segment of the procedure to be conducted. The next step is driving the drive assembly based on the predefined prediction profile of the operational variable to minimize a deviation between the operational variable and the prediction profile.
With the objects of the invention in view, there is also provided a drive system including a drive assembly, an automatic transmission, and an automatic clutch optionally connecting a torque transmission between the drive assembly and the automatic transmission, a first drive control loop for driving the drive assembly, and a second drive control loop for driving the automatic transmission. When a procedure having time segments is conducted, the second drive control loop predefines, for at least one time segment of the procedure, a prediction profile for an operational variable characterizing an operation of the drive assembly. The first drive control loop drives the drive assembly to set an operational variable based on the prediction profile.
According to a first aspect of the present invention, the object is achieved by a method for driving a drive assembly in a drive system. The drive system includes an automatic transmission and an automatic clutch that optionally couples the drive assembly to the transmission in order to transmit torque, the method includes the following steps:
a) sensing whether a procedure, in particular a gearshift operation, is to be conducted,
b) after it has been sensed that a procedure, in particular a gearshift operation, is to be conducted, predefining a prediction profile for an operational variable which characterizes the operating state of the drive assembly for at least one time segment of the procedure which is to be carried out, and
c) driving the drive assembly on the basis of the predefined prediction profile of the operational variable to minimize a deviation between the operational variable and the prediction profile is minimized.
In the present invention, a specific prediction profile of the operational variable that is to be adjusted is predefined for the drive system so that measures can have already been taken at an early time in order to be able to obtain a desired value of this operational variable at specific times. By reference to this prediction profile, it is therefore possible to perform pre-control, with the consequence that the actual characteristic of the operational variable, which is obtained, for example, during the execution of the gearshift operation has a profile with a significantly smaller deviation from the prediction profile, that is to say than is the case with the actual variable and the setpoint variable of the prior art. Such a procedure with the predefinition of a specific prediction profile can be used for a wide variety of procedures, preferably when shifting gears. Such a procedure also can be an acceleration procedure in which the engine torque is to be changed in a relatively short time by predefining a vehicle driver.
Because the driving states can change during the execution of such procedures, in particular also while shifting gears, for example because the driver actuates the acceleration pedal or a brake pedal during the execution, the prediction profile which is predefined for a specific procedure may no longer be suitable for the operational characteristics present at a given time. In order to be able to take into account such relatively short-term changes in the operational state, it is proposed that the method should also have the following steps:
d) after it has been sensed that a procedure, in particular a shift in gears, predefining at least one setpoint value of the operational variable, and
e) if the at least one setpoint value of the operational variable deviates from an assigned prediction value of the prediction profile, driving the drive assembly to minimize a deviation between the operational variable and the at least one setpoint value.
In this procedure, an additional setpoint value which defines a correction term by reference to the possibly present deviation from an assigned prediction value which is therefore determined for an identical time is therefore used, at least when necessary, to set or adjust the operational variable in a corrected fashion.
To do this, there may be provision, for example, for the step
e) including the following substeps:
e1) driving a first control point of the drive assembly on the basis of the prediction profile, and
e2) driving a second control point of the drive assembly based on a deviation between the at least one setpoint value and the associated prediction value of the prediction profile.
For example, the driving of the drive assembly on the basis of the prediction profile can include the driving of an air inlet system, which is assigned to the drive assembly, that can be embodied as an internal combustion engine.
Such air inlet systems have a relatively long adjustment time when they are driven, i.e. there is a certain delay between the driving of such an air inlet system and the desired adjustment behavior, i.e. the approaching of the actual value to the predefined value, i.e. as the result of the requirement to adjust, for example, a throttle valve and as a result of the fact that even when a throttle valve closes there is an air volume present in the following air intake manifold. Because, in accordance with the method of the invention of the instant application, which values of the operational variable are to be obtained at specific times has already been known for a relatively long time in advance by predefining the prediction profile, it is possible to eliminate the problems referred to above, also to provide, by delaying when driving, for example, an air inlet system, that the driving of the drive assembly on the basis of the prediction profile includes the following steps:
f) determining a reaction time of a control point that is to be driven for a specific drive time on the basis of at least one operating parameter, for example rotational speed, torque, intake air temperature, and intake manifold volume,
g) Based on the reaction time, which is determined for the specific drive time, determining a prediction value for a time, which follows the specific drive time by a time equal to the reaction time determined, by reference to the prediction profile, and
h) driving the control point at the specific drive time on the basis of the prediction value determined.
This means that a pre-control is performed here, i.e. at a current time a predefined value which is intended for the future is defined for the air inlet system so that at a later time the air inlet system is in a state which is predefined for this later time by reference to the prediction profile.
As already mentioned above, it is possible that correcting setpoint values that deviate from a prediction profile are predefined during the execution of a procedure. To be able to account for such correction variables within a short time, step e2) should include the driving of an ignition system and/or injection system and/or valve actuation system assigned to the drive assembly which is embodied as an internal combustion engine. The driving of these various systems constitutes a relatively rapid intervention into the drive system, i.e. a comparatively rapid reaction in comparison with the driving of the air inlet system is obtained during the changing of the operational variable.
Because this reaction is relatively fast, i.e. a predefined setpoint value can be taken into account relatively quickly, it is possible to provide that the step e) includes, at each specific drive time, the driving of the drive assembly on the basis of a setpoint value, assigned to the specific driving time, of the operational variable.
Therefore, it is not necessary to account for specific delays occurring between the driving and the reaction or for a setpoint value that is present only with a specific delay.
With the method according to the invention, the prediction profile can be predefined in an unchanged way.
In addition, it is possible for the procedure, in particular the gearshift operation, to be divided into a multiplicity of phases, and for the prediction profile to be capable of being varied for phases which are not yet relevant to driving.
The prediction profile that is defined in the method according to the invention can include at least one, preferably at least two, prediction supporting values for the operational variable. If a plurality of phases is provided, it is possible to provide that the prediction profile includes at least one, preferably at least two, prediction supporting values for each of these phases.
The precision of the engine control can be improved further if, in addition to the prediction supporting values that define the prediction profile, at least one, preferably a multiplicity of, prediction supplementary values is provided. The prediction supplementary values are obtained by interpolation or extrapolation including the at least one prediction supporting value.
The operational variable that is to be set or adjusted to a specific profile during the execution of the procedure can be the torque or the rotational speed of the drive assembly. In particular, it is possible that if the procedure is divided into a plurality of phases, the operational variable is the torque for at least one of these phases, and the operational variable is the rotational speed for at least a further phase of these phases.
In particular, if the procedure that is to be executed is a gearshift operation, the torque of the drive assembly is first minimized, in which case when this minimum is approached or reached a gear speed is disengaged and subsequently a new gear is engaged. According to the invention, the operational variable can be the rotational speed of the drive assembly only in a phase in which the torque of the drive assembly reaches the region of a minimum value.
In this way, after a previously selected gear speed has been disengaged, it is possible, by controlling the rotational speed, to change the rotational speed of the drive assembly to a desired value, which coincides with the rotational speed present at the input side of the transmission after the new gear speed is engaged. In this way, synchronization can already be performed at the engine end so that during the subsequent clutch engagement operation, the clutch is loaded only to a small degree. Also, when the clutch is not completely disengaged, it is possible to perform synchronization for the transmission in this way because the input side of the transmission also can be changed to the rotational speed corresponding to the new gear speed by adapting the rotational speed of the drive assembly with the clutch.
With the method according to the invention, it is also possible to provide for the prediction profile, and if appropriate the at least one setpoint value, to be generated in a drive control loop which is assigned to the automatic transmission, and to be transmitted to a drive control loop, assigned to the drive assembly, in order to drive the drive assembly.
According to a further aspect, the object of the invention mentioned at the beginning is achieved by a drive system, in particular for a motor vehicle, including a drive assembly, an automatic transmission, an automatic clutch, which optionally brings about a torque transmission connection between the drive assembly and the automatic transmission, a first drive control loop for driving the drive assembly, a second drive control loop for driving the automatic transmission, and if appropriate the automatic clutch.
When a procedure, in particular a gearshift operation, is conducted, the second drive control loop can predefine, for at least one time segment of the procedure which is to be carried out, a prediction profile for an operational variable that characterizes the operation of the drive assembly, and that the first drive control loop drives the drive assembly in order to set the operational variable on the basis of the prediction profile.
Here, in order to take into account short-term changes in the operating state, the drive system is also designed in such a way that the second drive control loop also determines, during the execution of the procedure, in particular the gearshift operation, at least one setpoint value for the operational variable, and that the first drive control loop also drives the drive assembly on the basis of the at least one setpoint value if there is a deviation between said setpoint value and a corresponding prediction value of the prediction profile.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a Method for driving a drive assembly in a drive system, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.